This invention relates to a system for playing a wagering game based on a drawing, and in particular, a system for determining whether wagers have been altered after winning game numbers are drawn.
Lottery and keno games are typical wagering games in which a gaming authority conducts periodic drawings of winning elements such as winning game numbers. In such games, each player selects a series of game elements, e.g., game numbers chosen from a set of numbers, which the player believes will be drawn during a subsequent drawing of winning game numbers from the set of numbers. For example, in a lottery game, a player may select six game numbers from the set of integers 1 through 40 which the player believes will match six winning game numbers drawn by the gaming authority. Similarly, in a keno game, a player may select 10 game numbers from the set of integers from 1 through 80 which the players believes will match 10 out of 20 numbers drawn by the gaming authority. Drawings for lottery games typically occur once or twice a week, while drawings for keno games can occur at intervals as short as several minutes.
Drawing games such as lottery and keno games are typically played using electronic gaming systems. Such electronic gaming systems include geographically dispersed gaming terminals for placing players"" wagers. The terminals are connected to a host computer that usually records wagering information relating to the players"" wagers in an electronic storage device such as a magnetic medium.
For security purposes, an electronic gaming system requires a mechanism for ensuring that existing wagering information is not altered after the drawing of winning game numbers to create a fraudulent wager containing game numbers that match the winning game numbers. The alteration may be any modification, deletion, addition or corruption of the wagering information. Several methods have been used to determine whether wagering information has been altered after a drawing of winning game numbers.
For games in which drawings occur once a day or less often, an electronic or printed copy of the wagering information for all wagers placed on the game can be made and secured at a remote location before the winning game numbers are drawn. At any time after the drawing, the secure copy of the wagering information can be compared to the wagering information stored in the host computer on a record-by-record basis to determine whether any alterations were made to the wagering information. This technique is time consuming, and is difficult to use with games in which drawings occur every few minutes.
A second technique involves use of an internal control system (ICS) connected to the host computer to perform auditing functions. In addition to recording the wagering information for every wager in the host computer, a copy of the wagering information for each wager is sent to the ICS. Before the winning game numbers are drawn, the ICS must assure that it has received a copy of all wagering information for the game. Thus, there must be no technical failures of the system or loss of communication between the gaming terminals and the host computer prior to the drawing. To perform the auditing function properly, the ICS must also be able to determine independently that the winning game numbers have not been drawn when the last wager is placed.
A third technique involves writing all wagering information to a fixed medium such as a write once removable media (WORM) drive. Once wagering information has been written to the WORM drive, it cannot be altered. This technique helps to prevent alteration of wagering information, but does not determine whether any alterations have been made prior to writing the wagering information to the WORM drive. A limitation of a WORM drive is that its use requires ensuring that all wagering information has actually been written to the WORM drive prior to drawing the winning game numbers.
In general, in one aspect, the invention features a system for determining whether wager data for players"" wagers placed on a drawing game have been altered after winning game numbers are drawn. A host computer stores the wager data and generates a first hash value for the wager data at a time prior to drawing the winning game elements, the host computer being capable of generating a second hash value for the wager data at a time subsequent to drawing the winning game elements for comparison to the first hash value. A verification device receives the first hash value for the wager data prior to drawing the winning game elements and receives the winning game elements.
Implementations of the invention may also include one or more of the following features. The wager data may include players"" game numbers and wager amounts.
The host computer may generate an intermediate hash value prior to generating the first hash value. The host computer may generate a transaction hash value for each of the players"" wagers. The host computer may generate a first digital signature to uniquely identify the host computer, and append the first digital signature to the first hash value.
The verification device may generate a combination hash value for the winning game elements and the first hash value, and transmit the combination hash value and the winning game elements to the host computer. The host computer may generate a check hash value for the winning game numbers and the first hash value, and compare the check hash value to the combination hash value. The verification device may generate a second digital signature to uniquely identify the drawing device, and append the second digital signature to the combination hash value.
The host computer may include a memory for storing the wager data and the first hash value. The system may further include a gaming terminal for generating the wager data. The system may further include a drawing device for drawing the winning game elements. The system may also include an auditing device in communication with the host computer for generating a third hash value for the wager data and comparing the first hash value to the third hash value.
In general, in another aspect, the invention features a method of detecting whether any of a plurality of stored wager data for players"" wagers placed on a drawing game has been altered after winning game elements are drawn. A first hash value for the plurality of stored wager data is generated before the winning game elements are drawn. A second hash value for the plurality of stored wager data is generated after the winning game elements are drawn. The first hash value is compared to the second hash value.
Implementations of the invention may also include one or more of the following features. The method may further include determining that at least a portion of the plurality of stored wager data has been altered based on a comparison of the first hash value and the second hash value. The method may also include transmitting the first hash value to an independent location before the winning game elements are drawn.
The first hash value and the second hash value may be generated using a one-way hashing function. The method may include generating an intermediate hash value based on a portion of the plurality of stored wager data prior to generating the first hash value. The method may also include generating a transaction hash value based on the stored wager data for each of the players"" wagers.
In general, in another aspect, the invention features a method of securing a plurality of wager data for players"" wagers placed on a drawing game. A wager data hash value for the plurality of wager data is generated at a first location. The wager data hash value is sent to a second location. The winning game elements are drawn. A combination hash value for the wager data hash value and the winning game elements is generated at the second location. The winning game elements and the combination hash value are transmitted to the first location.
Implementations of the invention may also include one or more of the following features. The method may include generating a check hash value for the wager data hash value and the winning game elements at the first location, and comparing the combination hash value to the check hash value. The method may also include appending a digital signature to the combination hash value at the second location.
An advantage of the present invention is that alterations of wager data after drawing the winning game numbers can be detected without having to make a copy of all of the wager data before the winning game numbers are drawn and without having to make a record-by-record comparison of the wager data before and after the drawing.
An additional advantage of the present invention is that alteration of wager data may be easily detected by a computer with limited processing and storage capacities.
A further advantage of the present invention is that wager data may be secured prior to drawing the winning game numbers for a game having any drawing frequency and using any drawing method, e.g., manual or electronic.
Other features and advantages of the invention will become apparent from the following detailed description, and from the claims.